1. Field of the Invention
The present invention relates generally to inductive amplifiers used to identify and trace a particular wire within a group of wires, and more particularly, to an inductive amplifier having a pair of terminals which can function to turn the amplifier on while simultaneously providing an amplified output signal to a telecommunications butt set.
2. Description of the Relevant Art
Inductive amplifiers, or tone detectors, are used by telecommunications service personnel to identify and trace a particular wire within a group or bundle of wires, without damaging the insulation surrounding each of such wires. Such inductive amplifiers are commonly used in conjunction with tone generators for tracing wires. The tone generator is coupled with a particular wire of interest to inject an audio frequency tone within such wire. The probe tip of the inductive amplifier is placed adjacent one of several wires to identify the particular wire conducting the injected audio tone. The inductive amplifier typically includes a built-in loudspeaker which can be used to produce an audible signal derived from the injected audio tone. In addition, the inductive amplifier typically includes a spring-biased pushbutton which may be depressed by a user to activate the amplifier and loudspeaker.
Several of the prior art inductive amplifiers which have been commercially available in the past have included a pair of ears extending from the housing of the inductive amplifier adjacent the end of the device opposite the probe tip. Examples of such prior art inductive amplifiers include the Aines Model 250SSP "Stationman" Speaker Probe sold by Aines Manufacturing Corp. of Ronkonkoma, N.Y., and the Model 200A "LineAid" inductive amplifier formerly sold by Progressive Electronics, Inc. of Mesa, Ariz., the assignee of the present invention. Each of the two ears includes a pair of electrically conductive plates extending parallel to each other and separated by a relatively thin insulator layer. By shorting the two opposing plates on one of such ears, the user can maintain the amplifier turned on without continually depressing the manually-operated pushbutton. The shorting of these two plates can be effected by applying an electrical alligator clip on such ear, simultaneously contacting both the upper and lower plates on such ear.
Telecommunications service personnel often carry upon their tool belt a rugged telephone handset having a pair of electrical alligator clips for connecting the handset to telephone wires to test communication lines. These service handsets are often referred to as "butt sets" in the industry, presumably because they have a hook for fastening the handset to a tool belt and tend to hang down along the service person's buttocks. The handset includes a microphone and an earphone, as well as a loudspeaker. When service personnel use inductive amplifiers, they often prefer to listen for the audible tone using their butt set. In those instances where a service person is working in cramped, noisy quarters, it may be difficult to hear the built-in loudspeaker clearly, and in this event, it is much easier for the service person to connect the butt set to the inductive amplifier, and to hold the butt set near his or her ear in order to monitor the tone.
As mentioned above, prior art inductive amplifiers have been provided with a pair of wings extending outwardly from the body of the amplifier housing. By applying one of the electrical alligator clips across the opposing plates of one of such wings, such plates are shorted together to turn the amplifier on. By applying the second electrical alligator clip of the butt set across the opposing electrical plates of the second wing, the butt set is electrically coupled into the output circuit of the amplifier for receiving the amplified audio output signal.
While such outwardly extending ears thereby serve to permit a service person to connect a butt set to such inductive amplifiers, such prior art inductive amplifiers are also subject to various disadvantages. For example, because such ears extend outwardly from both sides of the inductive amplifier housing and are relatively thin, they are often cracked or broken off altogether when the inductive amplifier is inadvertently dropped or bumped against another object. Moreover, because such ears have only a thin layer of insulation between the opposing conductive plates, moisture can sometimes bridge the gap between the two opposing plates and cause the inductive amplifier to drain current from the battery when not in use.
In addition, because such ears extend outwardly and are relatively flat, the electrical alligator clips of a butt set or shorting wire attached thereto are often inadvertently knocked off of such ears. Furthermore, because such ears project outwardly from the inductive amplifier housing, they are easily contacted by the hands of the user; while such contact poses no danger to the service person, the body of the service person acts like an antennae and picks up stray signals or feedback which can be introduced into the amplifier circuitry through such ears, causing false tones and/or oscillations to be heard by the user.
As indicated above, prior art inductive amplifiers provided with protruding ears include three or four conductive plates in order to facilitate the connection of a butt set to the inductive amplifier. However, the more electrical contacts that project from the inductive amplifier housing, the more likely it is that such contacts will be inadvertently shorted together or touched by a user's body to introduce oscillations.
Accordingly, it is an object of the present invention to provide an inductive amplifier adapted to be more easily connected with a telecommunications butt set while minimizing the likelihood that the electrical connectors of the butt set will be knocked loose from the inductive amplifier.
It is another object of the present invention to provide such an inductive amplifier adapted to be more easily connected with a shorting wire in order to maintain power to the amplifier without manual depression of a pushbutton while minimizing the likelihood that the electrical connectors of the shorting wire will be knocked loose from the inductive amplifier.
It is still another object of the present invention to provide such an inductive amplifier which minimizes the number of exposed electrical terminals extending from the housing of the amplifier while still permitting the connection of the aforementioned butt set or shorting wire thereto.
A further object of the present invention is to provide such an inductive amplifier which minimizes the likelihood of contact with the user's body to lessen the introduction of stray signals or oscillations into the inductive amplifier circuitry.
A still further object of the present invention is to minimize the likelihood of damage or breakage of exposed electrical terminals extending from the housing of the amplifier.
A yet further object of the present invention is to provide such an inductive amplifier which has less susceptibility to impaired performance due to contact with moisture.
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.